Now what? Cylinder, lock, bolt?


Anyone who doesn't deal with locking systems very often will quickly notice when talking to experts that they don't have the right terms. This leads to misunderstandings because the term “lock” is used but “cylinder” is meant. To prevent this from happening, we have compiled and explained the most important terms in this glossary.

Many of the definitions are clear and difficult to interpret. But things are different with modern names such as “access control system” or “locking system”. Whether a door can only be opened with a key or with a chip card is not determined per se by the two terms mentioned.


In order to be able to make a clear distinction between the terms, CouHome only uses the word “locking system” when it comes to systems with keys. If doors are to be opened using a chip card, Bluetooth or code lock, we call them access control systems. The clear distinction is helpful because locking systems do not require a power supply to the door, but access control systems require a power supply.


Scanning security – This indicates how difficult it is to obtain the information using suitable technical tools in order to create a duplicate key. It can be increased using recesses in several dimensions or embedded magnets.

Hinge Side – The side of a door where the hinges are normally visible.

Backset – The backset is the distance between the front edge of the lock (→ forend) and the centre of the → lock cylinder. It is important because the forend screw must be at least as long as the backset in order to lock the cylinder in the lock.

Double cylinder - It is a special type of → locking cylinder that can be operated from both sides with a key. A distinction is made between standard cylinders and those with → comfort functions.

Mortise lock - lock with latch and bolt according to DIN 18 251 for installation in various doors. Mortise locks can have a cam lock, tumbler or profile cylinder locking mechanism or can be mortice locks with a bathroom bolt. The most important components of a mortise lock are → latch, → faceplate, → bolt, change, follower, → lock case and tumblers.

Latch (or lock latch) - Part of the lock that protrudes from the lock when the door is open and is pushed into the lock by pressure on an inclined surface when the door is pushed shut or "slammed shut". If the door is completely closed, a spring presses the latch into the recess in the striking plate and thus keeps the door closed. This often happens with a clearly audible “click”. The latch can be pulled back using the door handle or with a key to open the door.

Same locking - If two cylinders have the same → locking (i.e. can be locked with the same key), this is called simultaneous locking. This makes sense if the garage and front door can be locked with the same key or if several rooms in a company should be able to be accessed by a specific group of people.

Convenience function - In unfortunate situations, it may be necessary to operate a lock from the outside even if a key is inside and may be twisted. Cylinders with a convenience function technically offer the possibility of being able to operate the lock independently of a key that may be inserted on the other side.

Knob – A usually immovable round handle on one side of the door so that it can be opened with a key after unlocking.

mechatronic – a portmanteau of mechanical and electronic that describes a technology in which mechanical and electronic components work together. In mechatronic → cylinders, for example, the electronics ensure that if the electronic registration is successful, the key is turned mechanically and the → bolt can be moved.

Multi-point locking – A locking device that secures a door at several points (points) using → latches, bars or bolts. It increases security because it makes it more difficult for attackers to break down the door.

Re-locking security - Describes the degree to which it is difficult to operate a locking cylinder with a key other than the associated key. Re-locking security can be achieved through a special shape of the key profile as well as through appropriate key profile controls, such as side control pins, balls or tilting elements. All measures to minimize wear in the locking cylinder and on the key also ensure a high level of relocking security.

Reide (key reide) – head or handle of the key.

Deadbolt - A metal rod in the lock that is moved when a key is turned in the cylinder to lock or unlock the door. There is a recess in the → striking plate of the door frame for this). Security doors can also have multiple bolts.

Locking system – a complete system consisting of cylinders, keys and (for electronic and mechatronic systems) hardware and software for programming and managing keys and cylinders. If systems with electronic locking cards are also referred to, they are often referred to as access control systems.

Locking - This refers to the configuration of the key and cylinder, which determines how the key must be designed so that it can be turned into the cylinder. If there are several cylinders for several keys that can be locked with these keys, this is referred to as → keying in common.

Locking system – The way the lock technology works. A distinction is made between mechanical and mechatronic.

Key bit – The part of the key that is inserted into the → lock cylinder and is “checked” by the cylinder to clear the cylinder core for rotation.

Strike plate – Mechanical, often metal, stable device in the door frame (frame) with recesses for the latch and bolt of the lock. It prevents the door from opening if the latch and/or bolt protrude into the recesses. As a security striking plate, it is connected to the masonry behind the frame using wall anchors. An electrical strike plate contact (bolt switch contact) can also be installed on the strike plate.

Lock cylinder – see → Cylinder

Lock – Mechanical, often metal unit that is built into the front of the door leaf. It usually consists of the → lock case, → faceplate, → latch and → bolt and recess for the → lock cylinder. Modern locks can also be operated electrically. The lock does not include → door handle and → cylinder. The lock secures the door from unauthorized opening.

Lock case – is the visible shell of a → lock when it is removed.

Key channel – opening and guidance within the → locking cylinder into which the key can be inserted.

Key Security – The difficulty of keys being copied without authorization and for unfair purposes. Key security is determined by the type of key (technical copy protection) and the availability of raw keys (free key profiles and patented (= protected) key profiles).

Security fitting - A door handle set consisting of the following parts: outer plate, inner plate, connecting element between outer and inner plate, door handle on the inner plate, any door handle or fixed knob or push handle (handle plate) on the outer plate, if necessary with an additional cover for the locking cylinder.

Security card – identification in credit card format that is issued for a → locking system or an individual → locking cylinder and only entitles the owner to obtain replacement keys and/or locking cylinders for the relevant → locking system or locking system.

Forend - front plate for mortise locks for carrying the → bolt and → latch out of the → lock case and for fastening the mortise lock in the door leaf with one or more fastening screws above and below the lock case.

Door hinge – metal hinge on the hinge side of a door, both in the door leaf and → door frame. Often with interlocking metal pins to prevent the door from being levered out. Door hinges with springs are able to close doors automatically.

Door handle - a handle on one or both sides of the door that, when pressed, pulls the → latch and thus allows the door to be opened. Alternative names are handle, buckle, and pusher.

Reversible key – a key that does not matter in which orientation it is inserted into the key channel. It has identical troughs and safety features on both sides of the beard.

Frame – frame in the masonry in which the door is hung via hinges and which accommodates the striking plate as a counterpart to the lock.

Access control – A system that ensures that only authorized people have access to certain areas and facilities. This can be ensured via locking systems or access control systems.

Access control systems - systems and products to protect against unauthorized access to sensitive areas such as offices, data centres, laboratories, cash registers, archives, production facilities, vaults, etc. In contrast to locking systems that use keys, access control systems also use chip cards and fully electronic authentication means, to check access authorizations. Readers must be installed for authentication.

Cylinder cover – Additional cover on the protective fitting to prevent the → locking cylinder or its core from being pulled out forcibly.

Cylinder or locking cylinder - Interchangeable part of a lock that uses suitable technology to check whether the key can be turned and thus the bolt or latch moved after inserting a key. In the case of mechanical cylinders, the test is often carried out using pins that have to be pressed in correctly through the key bit in order to be able to turn the lock cylinder core. The cylinder is locked in the → lock by a forend screw and can therefore only be changed when the door is open.


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